Production of potassium sulphate fertilizer material



June 8, 1937. R. E. PENNELL PRODUCTION OF POTASSIUM SUL PHATE FERTILIZER MATERIAL Filed June 18, 1956 Patented June 8, 193T e I e l UNITED STATES PATENT OFFIQE.

, PRODUCTION or Po'rAssIUM SULPHATE FERTILIZER. MATERIAL Robert E. Pennell, Anderson, S. 0.

Application June 18, 1936, SeriaLNo. 86,013

3 Claims. (Cl. 23-417) The present invention has for its object the kettle having a gas exit leading to a suitable production of fertilizer material containing sul- .absorbingdevice, such as a tower having a filling phate of potash as an important constituent. therein. Crude potassium chloride, (e. g. potas- Up to the present time, essentially all sulphate sium chloride of fertilizer. grade) is slowly added 5 potash and sulphate potash magnesia used for to the sulphuric acid, untilabout parts have fertilizer purposes are imported into the United been added. During the saidaddition which re- States although this country has a surplus of quired about 2 hours, the mixtureof said acid sulphuric acid and abundance of dolomitic limewith chloride iscontinuously agitated. 1 stone analyzing as high as 46% magnesium The kettleand its contents are then heated l0 carbonate and 52% calcium carbonate, as well as slowly, while continuing the agitation, until the 10 a good production of potassium chloride analyzmaterial in the kettle reached a temperature of ing as high as 62.5% K20. Except for the potash, 300 F. This heating was continued for about 3 these materials are in the center of the tobacco hours. and truck areas requiring fertilizers containing During these operations, nearly all of the hy- 1 water soluble magnesium and potash which is drochloric acid is removed leaving potassium chlorine free. The present cost per unit K in hydrogen sulphate in a more or less fused condi- KCl is 50, while the cost is 96 perunit in sultion. The mass was slowly heated in the kettle, phate potash magnesia (imported). It is imand the hydrochloric acid vapors given off were possible to manufacture sulphate of potash di- 1 .led to a scrubber of a suitable sort for absorp- 20 rectly as such economically in this country, altion of the gases. About 95% of the K61 was 2 though it is possible to manufacture sulphate converted into KHSO4 during this treatment. potash-water soluble magnesia fertilizer material I do not restrict myself to the details of this to a great advantage and profit as described in illustration. In other runs of the process, my process. This process has for its object the temperatures between 240 and 400 F. were used.

production of a fertilizer material containing pot- The potassium hydrogen sulphate, at 300 F., 25

ash practically free of chlorine in combination ,was a semi-liquid mass. with water soluble magnesia with calcium present d mp1 6 largely as gypsum as a conditioner. In this process the magnesium is changed from the The potassium acid sulphate can be treated carbonate to the. more valuable water soluble with dolomitic lime-stone, fo neutral D sulphate form, thus giving a very desirable fertitaSSiv-m S phate, magnesium sulphate and callizer t i l, cium sulphate, carbon dioxide being given off.

In accordance with the present invention, I Preferably about 3 Parts Of the hot potass um first t t potassium chloride ith sulphuric bisulphate, for example as coming from the kettle acid, but not in such proportions as to form the above referred is intimately m xed with 1 neutral-potassium sulphate. On the other hand, part of dolomitic lime-stone. The KHSO4 reacts I preferably employ such proportions asto give with the magnesium carbonate and with the calpotassium bisulphate, or at least a mixture apum bonate, to form sulphate. The treatproximating such composition. This potassium ment is best carried out by introduc t e d010- bisulphate is subsequently acted upon with other mitic lime-stone in powdered form into a mixer, 40 materials as given below,'to produce final fertiand adding th t potassium bisulphate in a lizers or final materials to which additional semi-liquid condit t a temperature of say fertilizing agents can be added or not as desired. The materials are Well miXed in a The following is given as the preferred mode illustratively of the type commonly used for mix- 5 of treating the original potassium chloride used, ing cement. The material is then placed in 4 to give a product consisting largely or substanstorage and the reaction continues to go on for tially of potassium hydrogen sulphate, say a week or two. Volumes of carbon dioxide The sulphuric acid can be. put into a reaction are liberated, and during the process o reactkettle having a gas outlet, and having a rather ing the carbon dioxide liberated gives the mawide outlet opening at the bottom for reaction terial a more or less porous condition. 50

products which consist largely of potassium bi- It will be understood that exhaust openings are sulphate. The step here referred to was, in a provided to remove the gases formed during the particular run, carried out in the following manreaction, both in the mixing device and the storner. Sulphuric acid, at room temperature, say age space.

17.2 parts of 61 B. acid, were placed in a closed As an example of above specific case:

When 2%; grams of the resulting salt are dissolved in 150 cc. of cold water with stirring and then Washed on filter up to 25 00., 97% of this material is found to be water soluble,

The analysis being as follows:

Percent 1. Moisture at 105 C 1.80 2. Residue (insoluble in cold water) 2.96

(Consisting principally of SiOz and insoluble with traces of dolomite and gypsum.)

Water solution 97.04% of total:

s03 found 43.22

and 6 correspond very closely to that of ZKZSOLMgSOLCaSOLQHQO You will note from above analysis that'3, 4, 5

showing however a purity of approximately 82%. The above C. P. tri-salt' should'contain "54.36%

K2804, 18.79% Mgsol, 21.23% casol d 5.62%

E20. The ferrous sulphate shown in the, above sample is high due to the fact that the KHSO4 was made in a wrought iron reaction kettle.

This would probably be much lower in a cast or duriron kettle.

The reaction taking place in mixing the KHSOi and in forming the complex sulphate salt is as follows:

In this reaction the magnesium and calcium in the dolomite, Mg, Ca (C092, is changedfrom the,

water insoluble condition to the more valuable water soluble form in the I 2K2SO4.MgSO4.CaSOi.2H2O

In making the KHSOi in the above case the K01 used analyzed 62.71% K20. The dolomite subsequently mixed with the KHSO4 analyzed 45-46% magnesium carbonate-and 50-52% calcium carbonate, and was finely ground all passing through150 mesh screen. 1

A saturated solution of. this salt was found to contain 4.65 grams per 100 cc. of water at a temperature'of -65 F. A saturated solution in boiling water was found to be 8.20 grams per cc. Considering this, it would seem that its use in the soil should result in reduced leaching, more even plant feeding, and also reduce the tying up of its potash as an insoluble silicate.

It is seen from above that the calcium sulphate in solution is far greater in this combination cium sulphates. lump of the crude material than would be found in a saturated solution of gypsum at these temperatures.

A portion of above salt was purified by taking up 15 grams in 100 cc. of boiling water, neutralized with ammonia, a few drops of H202 added, boiled, Fe and undissolved matter filtered out. The filtrate was evaporated with distilled water to near dryness three times and excess water poured from crystals each time which were then placed on filter to drain. The freshly prepared crystals were then micro-photographed-as shown on drawing accompanying present application. See Fig. 1 and Fig. 2.

It will be noted that these crystals shown unfder microscope are of uniform structure and needlelike or fibrous in character showing a combination of potassium, magnesium, and cal- On the drawing is also shown a as produced, showing honey-comb eifect of its set-up. See Fig. 3.

In another case 2 grams of the sample Were dissolved in 100 cc. of cold water by stirring. The

2.96% water insoluble matter was then removed by filtration. The entire filtrate containing 97.04% was evaporated practically to dryness,

leaving the crystals slightly moist. The different portions of these crystals were then examined under microscope and found to bepractically identical with crystals photographed above. I claim:--- I 1. A process of producing a dry'free-fiowing I bisulphate, in a hot dry condition,'with dolomite,

in such proportions as to substantially entirely react with the bisulphate, thereby converting the potash into a neutral salt in combination with magnesium and calcium as sulphates.

2. A process of producing a dry'free-flowing" fertilizer salt which comprises reacting upon potassium chloride with sulphuric acid in such prO- portions as to drive off most of the chlorine content of such chloride in the forin'of hydrochloric acid and leaving a material consisting principally of potassium bisulphate, and then reacting upon saidpotassium bisulphate, in a hot dry condition,

with dolomite, in such proportions as to substantially entirely react with the' bisulphate, thereby converting the potash into a neutral salt in combination with magnesium and calcium as sulphates.

3. A new fertilizer material, as produced in claim 1, comprising a triple salt of potassium, magnesium, calcium, sulphates coresponding substantially to the formula 2K2SO4.MgSO4.C2.SO4.2H20.

ROBERT E. PENNELL. 

